Al-guided microstructural evolution, mechanical properties, and oxidation behavior of CoCrNiNb0.3Alx high-entropy alloys

In this study, Al was added to a CoCrNiNb 0.3 high-entropy alloy, and the effects of this addition on the microstructure, mechanical properties, and high-temperature oxidation behavior at 900 °C of CoCrNiNb 0.3 Al x multi-component alloys (x = 0, 0.05, 0.1, 0.15, 0.2) were investigated. The alloy consists of an FCC solid solution matrix, a C14 Laves phase. As the Al content increased, the yield strength increased monotonically with Al content, from 1003.4 MPa for Al0 to 1470.7 MPa for Al0.2. The Al0.05 alloy exhibited enhanced strength while retaining compressive plasticity comparable to that of the Al0 alloy. With a further increase in Al content, the fracture strain gradually decreased to 23.3% for the Al0.2 alloy. The Al0.15 alloy achieved the best oxidation resistance, with a mass gain of 0.1781 mg/cm 2 after 100 h at 900 °C approximately 77% lower than that of Al0. The oxidation cycle analysis of the Al0.15 alloy indicated that the continuous Al 2 O 3 -rich oxide layer improved the oxidation resistance of the alloy. The addition of an appropriate amount of Al enhanced oxidation resistance while maintaining excellent mechanical properties, providing valuable insights for the design of high-performance multi-principal component alloys.